A&A 473, 323–328 (2007) Astronomy DOI: 10.1051/0004-6361:20077314 & c ESO 2007 Astrophysics ELODIE metallicity-biased search for transiting Hot Jupiters IV. Intermediate period planets orbiting the stars HD 43691 and HD 132406 R. Da Silva1,S.Udry1, F. Bouchy3, C. Moutou2, M. Mayor1,J.-L.Beuzit5, X. Bonfils5,X.Delfosse5, M. Desort5, T. Forveille5, F. Galland5,G.Hébrard3, A.-M. Lagrange5, B. Loeillet2,C.Lovis1,F.Pepe1, C. Perrier5, F. Pont1, D. Queloz1,N.C.Santos1,4, D. Ségransan1,J.-P.Sivan2, A. Vidal-Madjar3, and S. Zucker6 1 Observatoire Astronomique de l’Université de Genève, 1290 Sauverny, Switzerland e-mail: [email protected] 2 Laboratoire d’Astrophysique de Marseille, UMR6110 CNRS, Université de Provence, Traverse du Siphon, BP 8, 13376 Marseille Cedex 12, France 3 Institut d’Astrophysique de Paris, UMR7095 CNRS, Université Pierre & Marie Curie, 98bis bd Arago, 75014 Paris, France 4 Centro de Astrofísica, Universidade do Porto, Rua das Estrelas, 4150-762 Porto, Portugal 5 Laboratoire d’Astrophysique de Grenoble, BP 53X, 38041 Grenoble Cedex, France 6 Department of Geophysics and Planetary Sciences, Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Tel Aviv 69978, Israel Received 16 February 2007 / Accepted 4 July 2007 ABSTRACT We report here the discovery of two planet candidates as a result of our planet-search programme biased in favour of high-metallicity stars, using the ELODIE spectrograph at the Observatoire de Haute Provence. One candidate has a minimum mass m2 sin i = 2.5 MJup and is orbiting the metal-rich star HD 43691 with period P = 40 days and eccentricity e = 0.14. The other planet has a minimum mass m2 sin i = 5.6 MJup and orbits the slightly metal-rich star HD 132406 with period P = 974 days and eccentricity e = 0.34. Additional observations for both stars were performed using the new SOPHIE spectrograph that replaces the ELODIE instrument, allowing an improved orbital solution for the systems. Key words. stars: individual: HD 43691 – stars: individual: HD 132406 – planetary systems – techniques: radial velocities 1. Introduction (Fischer et al. 2004), which monitors nearly 2000 main-sequence and subgiant stars. Another project was conducted by our team Following the first publications suggesting the metal-rich nature with the ELODIE spectrograph at the Observatoire de Haute of stars hosting giant planets in close orbits (Gonzalez 1997, Provence (Da Silva et al. 2006). From a sample of more than 1998), numerous studies on this theme have been published in a thousand solar-type stars, we selected the most metallic ones recent years (Santos et al. 2001, 2004; Fischer & Valenti 2005; after the first measurement to monitor their radial velocities. Gonzalez 2006). With the increasing number of known planets, Our programme has already yielded the detection of four Hot statistical studies were able to verify that the frequency of stars Jupiters, with periods between 2.2 and 6.8 days and minimum hosting a planetary companion is highly correlated with the stel- masses between 1.0 and 2.1 MJup, orbiting the stars HD 118203 lar metallicity. The results show that the probability of finding and HD 1491431 (Da Silva et al. 2006), HD 189733 (Bouchy a close-in giant planet is about 25–30% for the most metal-rich 1 / et al. 2005), and HD 185269 (Moutou et al. 2006). stars ([Fe H] > 0.3) and only 3% for stars with solar metallicity. For the star HD 189733, additional photometric measure- The extrasolar planet search biased in favour of high-metallicity ments have led to the observation of a planetary transit, making stars can thus rapidly lead to the discovery of planets in short- possible the determination of some parameters of the compan- P < period orbits, the so-called Hot Jupiters ( 10 days), increas- ion, such as mass, radius and mean density (Bouchy et al. 2005; ing the chances of finding planetary transits. The identification Bakos et al. 2006; Winn et al. 2007). This system is our best re- of planets transiting bright stars provides a powerful approach to sult, a very good example of what we expect to obtain with our determine fundamental constraints on the mechanisms of planet programme, and revealed to be of particular interest for further formation, the physical properties of the exoplanet, and the ge- studies. Deming et al. (2006) analysed the infrared thermal emis- ometry of the system. sion during an eclipse of HD 189733 b using the Spitzer Space Based on these assumptions, a few programmes have Telescope (Werner et al. 2004) and determined the brightness been initiated with the aim of looking for planets orbiting temperature of the planet at 16 µm. Knutson et al. (2007), per- high-metallicity stars. One of them is the N2K consortium forming observations with Spitzer at 8 µm, were able to con- struct a map of the temperature distribution of HD 189733 b, Based on radial velocities collected with the ELODIE spectro- graph mounted on the 193-cm telescope at the Observatoire de Haute 1 The planet around HD 149143 was independently discovered by Provence, France. Additional observations were made using the new Fischer et al. (2006) and the one orbiting HD 185269 was also pub- SOPHIE spectrograph (run 06B.PNP.CONS) that replaces ELODIE. lished by Johnson et al. (2006). Article published by EDP Sciences and available at http://www.aanda.org or http://dx.doi.org/10.1051/0004-6361:20077314 324 R. Da Silva et al.: ELODIE metallicity-biased search for transiting Hot Jupiters. IV. estimating a minimum and a maximum brightness temperature Table 1. ELODIE and SOPHIE radial velocities of HD 43691. All val- at this wavelength. Fortney & Marley (2007) analysed the mid ues are relative to the solar system barycentre. The uncertainties corre- infrared observations of HD 189733 and suggested a possible spond to the photon-noise errors. presence of water vapor in the atmosphere of the planetary com- panion. Observations with the Hubble Space Telescope have also JD − 2 400 000 RV Uncertainty been proposed in order to perform precise measurements of the [days] [km s−1][kms−1] size and the orbital inclination angle of HD 189733 b (Pont et al., ELODIE measurements in preparation). 53 333.6255 −29.123 0.011 In this paper, we report the discovery of two new planet can- 53 337.6057 −29.098 0.012 didates resulting from our ELODIE planet search programme bi- 53 398.4118 −29.015 0.012 ased towards metal-rich stars: a 2.5 Jupiter-mass planet orbiting 53 690.6694 −28.945 0.013 the star HD 43691 with period P = 40 days, and a 5.6 Jupiter- 53 692.6430 −28.962 0.013 mass planet in a long-period orbit of P = 974 days around the 53 693.6240 −28.983 0.014 star HD 132406. Such results are complemented by additional 53 714.5653 −28.912 0.014 measurements made using SOPHIE (Bouchy et al. 2006), the 53 715.5590 −28.903 0.015 new spectrograph that replaces ELODIE. 53 718.5549 −28.904 0.013 53 719.5681 −28.885 0.010 The radial velocity observations that have led to these results − are described in Sect. 2. The observed and derived parameters 53 720.5323 28.853 0.017 53 721.5123 −28.892 0.018 of the star HD 43691 together with the orbital solution adopted 53 722.5237 −28.907 0.015 are presented in Sect. 3. The same are presented in Sect. 4 for 53 728.4315 −28.969 0.018 the star HD 132406. In Sect. 5 we discuss the present and future 53 749.5333 −28.989 0.014 status of the observational programme. 53 750.4982 −28.958 0.014 53 756.4444 −28.840 0.018 53 808.2808 −29.091 0.012 2. Observations 53 809.2850 −29.087 0.009 53 839.3031 −28.960 0.019 The HD 43691 and HD 132406 stars are both targets in our − “ELODIE metallicity-biased search for transiting Hot Jupiters” 53 870.3405 28.881 0.017 53 872.3456 −28.923 0.020 survey (Da Silva et al. 2006), conducted from March 2004 un- til August 2006 with the ELODIE spectrograph (Baranne et al. SOPHIE measurements 1996) on the 193-cm telescope at the Observatoire de Haute 54 044.6274 −28.980 0.003 Provence (France). In this programme we essentially searched 54 051.6411 −28.830 0.004 for Jupiter-like planets orbiting metal-rich stars, assuming that 54 053.5968 −28.854 0.003 54 078.6009 −29.059 0.004 such stars are more likely to host giant planets. − After obtaining the first spectrum of HD 43691 and 54 079.4859 29.040 0.004 54 080.4572 −29.018 0.004 HD 132406, we verified the high metallicity of these stars from 54 081.4440 −28.993 0.003 a calibration of the surface of the ELODIE cross-correlation 54 087.4744 −28.858 0.004 functions (Santos et al. 2002; Naef 2003). After three measure- 54 088.5858 −28.872 0.004 ments, we could clearly see in both stars a significant radial ve- 54 089.6137 −28.846 0.004 locity variation. We therefore conducted follow-up observations 54 142.4798 −29.064 0.004 with ELODIE, and we obtained 22 spectra of HD 43691 from 54 148.4607 −29.089 0.004 November 2004 (JD = 2 453 333) to May 2006 (JD = 2 453 872), 54 151.4010 −29.065 0.004 and 17 spectra of HD 132406 from May 2004 (JD = 2 453 152) 54 155.4284 −28.981 0.004 to June 2006 (JD = 2 453 900).